The present disclosure relates to a liquid crystal display including a liquid crystal display element having a liquid crystal layer formed in a sealed-off state between a pair of substrates provided with alignment films on mutually facing sides thereof, and to a method of manufacturing the liquid crystal display.
In recent years, liquid crystal displays (LCDs) have been frequently used as display monitors in liquid crystal TV sets, notebook-sized personal computers, car navigation systems, etc. The liquid crystal displays are classified into a variety of display modes (systems) according to the molecular alignment (orientation) of liquid crystal molecules contained in a liquid crystal layer sandwiched between substrates. As one of the display modes, for example, a TN (Twisted Nematic) mode is well known in which the liquid crystal molecules are aligned (oriented) in a twisted state in the condition where no voltage is impressed thereon. In the TN mode, the liquid crystal molecules have a positive dielectric anisotropy, i.e., a property such that the dielectric constant in the major axis direction of the liquid crystal molecule is greater than the dielectric constant in the minor axis direction. As a result of this, the liquid crystal molecules are arranged in a line in the direction perpendicular to the substrate surface while the oriented azimuths of the liquid crystal molecules are sequentially rotated in planes parallel to the substrate surface.
On the other hand, an increasing attention has been paid to a VA (Vertical Alignment) mode in which liquid crystal molecules are oriented (aligned) vertically to the substrate plane in the condition where no voltage is impressed thereon. In the VA mode, the liquid crystal molecules have a negative dielectric anisotropy, i.e., a property such that the dielectric constant in the major axis direction of the liquid crystal molecule is lower than the dielectric constant in the minor axis direction. Consequently, a wider viewing angle can be realized in the VA mode as compared with the TN mode.
In a liquid crystal display in such a VA mode, when a voltage is impressed thereon, the liquid crystal molecules of a negative dielectric anisotropy having been aligned in the direction vertical to the substrates respond to the voltage in the manner of falling down to be parallel to the substrates, thereby permitting transmission of light therethrough. However, the liquid crystal molecules having been aligned vertically to the substrates are tilted in arbitrary directions. Upon application of a voltage, therefore, the alignment of the liquid crystal molecules is disturbed. This has been a cause of worsening the response characteristic to voltage.
In view of this, in order to enhance the response characteristic, technologies for regulating the direction in which the liquid crystal molecules fall down in response to a voltage have been investigated. A specific example of the technologies is a technique (light alignment film technique or photo-alignment technique) in which a pre-tilt is given to liquid crystal molecules by use of an alignment film formed by irradiation with linearly polarized UV light or irradiation with UV light from an oblique direction relative to the substrate plane. As the light alignment film technique, there has been known, for example, a technique in which a film formed from a polymer including a chalcone structure is irradiated with linearly polarized UV light or irradiated with UV light from an oblique direction relative to the substrate plane, whereby double bond portions in the chalcone structures are cross-linked to form an alignment film (refer to Japanese Patent Laid-open No. Hei 10-087859, Japanese Patent Laid-open No. Hei 10-252646, and Japanese Patent Laid-open No. 2002-082336). In addition, there has also been known a technique in which an alignment film is formed by use of a mixture of a vinyl cinnamate derivative polymer and a polyimide (see Japanese Patent Laid-open No. Hei 10-232400). Further, there has been known, for example, a technique in which a film containing a polyimide is irradiated with linearly polarized light having a wavelength of 254 nm to decompose a portion of the polyimide, thereby forming an alignment film (see Japanese Patent Laid-open No. Hei 10-073821). Besides, as a peripheral technique of the light alignment film technique, there has been known a technique in which a film of a liquid-crystalline polymer compound is formed on a film of a polymer containing a dichromatic photo-reactive building block such as an azobenzene derivative which film has been irradiated with linearly polarized light or irradiated with oblique light, thereby forming a liquid-crystalline alignment film (see Japanese Patent Laid-open No. Hei 11-326638).
In addition, there has been known, from Japanese Patent Laid-open No. 2011-095696, a liquid crystal display having a liquid crystal display element including a pair of alignment films provided on mutually facing sides of a pair of substrates, and a liquid crystal layer containing liquid crystal molecules having a negative dielectric anisotropy, wherein at least one of the pair of alignment films contains a cross-linked or deformed compound obtained by cross-linking or deforming a polymer compound having a cross-linkable functional group as a side chain, and the liquid crystal molecules are given a pre-tilt by the cross-linked or deformed compound.